The newest therapy for heart failure is the administration of beta-blockers. The results have been gratifying, but the mechanism is unknown. In fact, it seems paradoxical that a drug which "weakens" cardiac contraction should improve heart failure. The investigators will conduct an experiment designed to investigate the mechanism by which beta-blockers improve the syndrome. The hypothesis is that beta-blockers reverse a counter-productive metabolic picture caused by beta-stimulation in patients with heart failure. The counter-productive picture consists of excess levels of fatty acids, excess oxidation of fatty acids, and impaired oxidation of glucose. Beta-blockers reverse these changes. The investigators will recruit 16 patients, and treat some of them with beta-blocker, then study them all (before and after) by PET scanning with mock substrates.